University looking for a launch date

I'm a part of a university team looking for a launch opportunity for our 2 stage "I" class rocket somewhere within a reasonable days drive of salt lake city utah. All design members and participants on the project are TRA or NAR level 1 or higher certified and we fly under TRA research launch rules due to our sustainer motor being a de-certified motor. desirable dates include March to mid April 2020. I've tried checking a few places but so far most places I've checked don't seem to fly during early spring or lack the waiver. We require a 20k foot agl waiver for the project as projected is 17k feet. Any guidance or help on a possible venue for flying our rocket is appreciated. Comments or Private messages are fine for contact as I check here regularly.

NCR will be flying out @ the North Site in April. On the Pawnee, plenty of waiver. A few hours East on I-80 (6 to 8). COME ON DOWN..... Contact Joe Hinton. Several university teams have flown here, the welcome mat will be out. BTW tell us about your project!

TimothyG said:

we fly under TRA research launch rules due to our sustainer motor being a de-certified motor.

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Is it decertified because the certification expired, or the certification was taken away? If it's the second, I believe it's not allowed under TRA research rules.

That’s a great question. We are flying a long burn AeroTech G motor we got from a friend. It’s one of the new ones that had temperature issues. We’re trying to handle this by minimizing contact between the motor and any glued joints as well as drastically reduced surface contact to reduce heat transfer rate between motor casing and airframe.

TimothyG said:

That’s a great question. We are flying a long burn AeroTech G motor we got from a friend. It’s one of the new ones that had temperature issues.

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I found a post on the Tripoli FB page from Steve Shannon (Tripoli president) that these are still flyable as research motors. This is assuming it's the G8 and not something else.

djs said:

I found a post on the Tripoli FB page from Steve Shannon (Tripoli president) that these are still flyable as research motors. This is assuming it's the G8 and not something else.

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That’s right. And please watch for and report any signs of damage to your motor mount from motor heat. We made a mistake in certifying them in the first place because the outside of the case exceeds NFPA 1125 temperature limits, but the NFPA committee is hoping to collect data to either support or refute a proposal to raise those limits.
And don’t get burned.
I don’t think that is a real risk but they do get hot.

Thanks for the update, I had started searching for information in a mild panic after seeing that as we built our entire project around attempting to get 20 seconds of burn time with our final attempt. Our for score attempt however will be the CTI I175 to the Aerotech G8.
We would be happy to share our motor mount arrangement and how it stands up after the flight. However our motor mount has less than a square inch of surface contact with the motor by design. So what data we get should be taken with a large grain of salt.

Have you had experience igniting the G008 in a single stage configuration? Having burned two, I can say with confidence that they are difficult to light....and they are REALLY low thrust, so the sustainer must be REALLY light in order to stay somewhat vertical under thrust.

Without knowing more, your group has two challenges that jump out at me.

1. Finding an igniter that is small enough to fit through the tiny nozzle, low enough current to work with your electronics, and "hot" enough to light the G8 is a real challenge that should not be overlooked.

2. Designing a 29mm diameter sustainer that's light enough and has the proper stability to stay vertical through the sustainer burn, yet strong enough to endure the I175 boost won't be easy. Long burn sustainers are great fun, but if you don't have a sufficient thrust:weight ratio, they'll weather cock (tip into the wind) while still under thrust. For the G8, an "ideal" thrust:weight ratio of 5:1 would put your loaded sustainer weight at .359 lbs. The G8 weighs .339lbs, so that leaves 0.02 lbs, or 1/3 of an ounce for airframe weight...not likely. At a 3:1 thrust:weight ratio, which would likely work fine but result in some weather-cocking with any magnitude of upper level winds, the loaded sustainer would weigh 0.6lbs, allowing for an airframe weight of 0.2lbs or ~3.2 ounces...possible at least.

Sounds like a fun project; but it will be a real challenge! The two items above might make executing said project difficult (but I didn't say impossible)!

Eric, is a G8 harder to light than an F10? I had no problems lighting an F10 with an ematch and a little black powder enhancement.

Also, I’m not sure I follow the idea of weathercocking in flight. Off the pad, yes. But higher in the air? The rocket should come up to lateral speed and move with the wind rather quickly. Unless you mean weathercocking at layer changes, where upper air winds change speed/direction. But even so, the rocket is already at speed. On a G8, the sustainer won’t continually accelerate. It will come up to the speed where drag and gravity balance the thrust and hold there.

Which where the gravity turn bites you.

Charles_McG said:

Eric, is a G8 harder to light than an F10? I had no problems lighting an F10 with an ematch and a little black powder enhancement.

Also, I’m not sure I follow the idea of weathercocking in flight. Off the pad, yes. But higher in the air? The rocket should come up to lateral speed and move with the wind rather quickly. Unless you mean weathercocking at layer changes, where upper air winds change speed/direction. But even so, the rocket is already at speed. On a G8, the sustainer won’t continually accelerate. It will come up to the speed where drag and gravity balance the thrust and hold there.

Which where the gravity turn bites you.

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Hi Charles,

In my experience, YES the G8 is harder to light than the F10. Now, I have a somewhat limited sampling, as follows. I've only flown one F10, but according to my Flight Log, it had "instant ignition from a Firestar FS-12".

Regarding the G8, I've only burned them in the Aerotech Phoenix rocket glider...I'm not sure I'd put one in a conventional rocket...this is a motor that may struggle to lift its own weight. The first one I flew lit fine, albeit with a slow startup (it seemed somewhat contrary to the published initial thrust spike). The second one was to be a 5 way Phoenix salvo at LDRS this year. Of the five that we attempted, only two lit. Of those two, one didn't have enough thrust to move the Phoenix, and the other had just enough to clear the launch rail but not enough thrust to sustain flight. Again, the initial thrust seemed to be lacking. Comparing to the 32mm G12... which has more than enough thrust. That said, I think the G008 is a really cool motor; just ultra low-thrusting and a bit finicky.

Regarding weather-cocking, the lower the rocket's velocity (vertical) and/or the higher the wind's velocity (horizontal), the more likely the rocket is to tilt into the wind. I'd say this happens regardless of altitude, except generally the greater the altitude, the greater the velocity of wind shear. Therefore, even if the sustainer lights while pointed relatively vertical, the low thrust of the G8 (or equivalent) will produce a relatively low vehicle velocity, which will be more susceptible to wind shear; despite the fact that there is initial velocity thanks to the boost phase. In other words, weather-cocking happens continually throughout flight, not just a motor startup or zero velocity.

ECayemberg said:

Regarding weather-cocking, the lower the rocket's velocity (vertical) and/or the higher the wind's velocity (horizontal), the more likely the rocket is to tilt into the wind. I'd say this happens regardless of altitude, except generally the greater the altitude, the greater the velocity of wind shear. Therefore, even if the sustainer lights while pointed relatively vertical, the low thrust of the G8 (or equivalent) will produce a relatively low vehicle velocity, which will be more susceptible to wind shear; despite the fact that there is initial velocity thanks to the boost phase. In other words, weather-cocking happens continually throughout flight, not just a motor startup or zero velocity.

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Weathercocking in wind shear I can understand. I have a mental image of wind shear happening in relatively narrow (vertically) bands with smoothly flowing air in between. I don't understand further weathercocking in the middle of laminar air flow (net AoA should be zero). But my mental model may be off - maybe wind shear zones are thicker than I imagine? Or less sharply defined?

Anyway, I don't think you can ignore the gravity turn in a long, slow sustainer like this (either). After watching my Ute Tomahawk with a G115-F10, I'm going to stick with Mellows. The last 4 seconds of that F10 burn were nerve-wracking to watch. Luckily, the sustainer slowed down enough -during- the burn that it didn't zipper. Or I'll figure out a way to add 'verticality augmentation', like vectored thrust, or forward canards, or RCS.

Charles_McG said:

I don't understand further weathercocking in the middle of laminar air flow

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I'm not an aerospace engineer, but it's been my understanding that things like T:W ratio, CP, etc, are really only rough estimates and rules of thumb to what's really happening. Like most estimates, they fall apart sometimes when you get to the edge cases. And without wind tunnel testing and/or airflow sensors on a flight, it's hard to know how "laminar" the flow really was. We've all seen rockets that went "wobbly" mid flight for inexplicable reasons...

Second stage decelerates for the first 7 seconds of burn time. We aren’t looking for acceleration from the sustainer just retained velocity. First and second stage are 38mm mach1 rocketry fiberglass. Very thin very light.

TimothyG said:

Second stage decelerates for the first 7 seconds of burn time. We aren’t looking for acceleration from the sustainer just retained velocity. First and second stage are 38mm mach1 rocketry fiberglass. Very thin very light.

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But in this case, why not just do a boosted dart?

Rules dictate a two stage rocket. Heavier objects are a bit more difficult in my experience to bring back safely and we are not funded well enough to be producing or procuring specialty parachutes that can pack down small enough for a heavy dart. We have no GPS due to cost and instead are relying on mylar reflective streamers and picky launch weather requirements and a few very experienced students for spotting. Funding is tight for us so we are making due with what little we can procure and what we already have.

Is the 20s of thrust time really important, or can you back off of that? A CTI G33 (29mm, 3G) will be easy to light, smoky enough to be easier to track, and is still relatively easy to find. Also still certified so you don't need a TRA EX launch.

We ran hundreds of comparisons using every published as current Aerotech and CTI motor that would fit our airframe over the course of a weekend through Open Rocket and RockSim. With our airframe design we came up with a hand full of finalist and from there went based off of what would be realistically possible given our materials on hand and current budget. The CTI booster motor was the most gentle big "I" motor we found that also had an acceptable thrust curve to allow for our separation arrangment. There are a number of other considerations that came in to play as well but I didn't start this thread to discuss our entire project.

Case study for your consideration.
H295-H53.

https://forums.rocketshoppe.com/showthread.php?t=17931&page=1&pp=10

My GPS tracker failed during flight prep, so I flew with a Mylar streamer. Which I’ve done to 2000’.

4000’ was harder.

Beautiful rocket Charles. We ran that H combination through but given the rules in combination with our requirements of the airframe, it's a very low performer comparatively. We ran every single motor, from both Aerotech and CTI, suitable for use as a booster in combination with every single motor we found suitable for a sustainer as a combination through simulations to select our setup and few came close to the same range as what we settled on. The top 5 performers we simulated all used the CTI I175 motor as a booster with a modest delay followed by the longest burning motors possible. The only exception to this series of simulations was use of a long burn dual thrust I impulse, booster motor. However these are challenging due largely in part to the dual thrust creating an opportunity for early drag separation while still under power. In the end the largest possible portion of points in this competition belong to the altitude portion where your points go up with altitude to no limit. Two of the few rules that heavily dictate methods and design are "two stage required" and impulse limit of a 100% "I" motor.

I was pointing out the challenge of recovery. That rocket only got one flight.

TimothyG said:

impulse limit of a 100% "I" motor.

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Is this total installed impulse, or per motor/stage?

Charles_McG said:

I was pointing out the challenge of recovery. That rocket only got one flight.

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Wait, wait...

Salt flat, rather than Midwest swamp. Okay, that will help.

Still, 38mm airframe and streamer at >10 kilofeet. Challenging.

I still think you’re underestimating the amount of rotation you’ll see during that long burn - but it should be a cool flight if it lights. I love the idea of long burn sustainers.

What velocity do the sims say it lines out at?

Oh, and motor deploy or altimeter?

I agree 100% with Charles, this is the kind of flight where what the sim says and what actually happens may be radically different. Personally, I would not have used the G8 in this application.

That said, best of luck. Please give us an update after it flies.

mikec said:

Personally, I would not have used the G8 in this application..

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My concern on this one is that the design requirements seem to be less "engineering challenge" and more "hope for a perfect confluence of events" to work properly? @TimothyG - what is your feeling?

djs said:

My concern on this one is that the design requirements seem to be less "engineering challenge" and more "hope for a perfect confluence of events" to work properly? @TimothyG - what is your feeling?

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I dunno, I learned an awful lot from my school projects that depended on a perfect confluence of events. I suspect the winner will be one of the less optimistic teams. But I'm old and jaded.

If it was easy it wouldn’t be a competition. One thing we’ve tempered into our group is a willingness to not fly when conditions aren’t conducive to the planned flight.

Its too late now but for future projects, contact the community (us) as early as possible. I know if you'd asked, I would have let you borrow my eggtimer GPS tracker. I also have 2x G25W motors that I have no plans for. 25N average thrust with 5.3second burn. I would have just given you those motors since they were given to me.

edit: removed the part about certification. I'm not sure they're certified any more and they stopped production about 2006 or so.

TimothyG said:

One thing we’ve tempered into our group is a willingness to not fly when conditions aren’t conducive to the planned flight.

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Are you planning to fly a weather balloon to determine what the winds aloft are like? Wind speed on the ground may tell you very little about conditions at staging altitude.

mikec said:

Are you planning to fly a weather balloon to determine what the winds aloft are like? Wind speed on the ground may tell you very little about conditions at staging altitude.

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No that’s a waste of a good balloon. There’s nice government software out there for high altitude winds. Works great for out balloon flights and gives nice predictions for anything high altitude for our rockets. GAS team introduced us to the software and I can’t recall the name.

the reason we don’t borrow hardware anymore is if it’s lost or damaged the balance due comes from students not the school. Most students can’t afford a gamble like that. I personally have thousands in hardware sitting in the desert or the trash as a result of learning this.

TimothyG said:

No that’s a waste of a good balloon. There’s nice government software... gives nice predictions for anything high altitude for our rockets.

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OK, but predictions are not measurements.

I think we've expressed our concerns, and I get it that you think you've addressed all of them. Again, best of luck.